The present invention relates to a method for producing a carbonyl compound by dehydrogenating an alcohol. More particularly, it relates to a method for producing a carbonyl compound by dehydrogenating an alcohol in the presence of a complex compound catalyst comprising ruthenium and a specific organic phosphine. A suitable example to which the method of the invention is applied is production of xcex3-butyrolactone from 1,4-butanediol.
Hitherto, there have been proposed several methods for producing a carbonyl compound by dehydrogenating an alcohol in the presence of a complex compound catalyst wherein a specific transition metal and a specific organic phosphine are combined. For example, a reaction of obtaining a lactone compound by dehydrogenating a diol using iridium-triisopropylphosphine complex, ruthenium-triphenylphosphine complex and rhenium-triisopropylphosphine complex as catalysts is described in J. Orgmet. Chem., 429 (1992) 269-274, a reaction of obtaining a lactone compound by dehydrogenating a diol using ruthenium-triphenylphosphine complex different from the above as a catalyst is described in J. Org. Chem., 1987, 52, 4319-4327 and Tetrahedron Let., 1981, 22, 5327-5330, and a reaction of obtaining a lactone compound by dehydrogenating a diol using ruthenium-bis(diphenylphosphino)butane compound complex as a catalyst is described in Chem. Soc. Japan, 1982, 1179-1182.
However, in these reactions, the dehydrogenation of the alcohol substrate is accelerated by the presence of a hydrogen acceptor such as acetone in the reaction system, and the catalyst activity is remarkably decreased when the hydrogen acceptor is not present.
In Bull. Chem. Soc. Jpn., 61, 2291-2294 (1988), a reaction of dehydrogenating methanol using rutheniumethyldiphenylphosphine complex or ruthenium-diethyl-phenylphosphine complex as a catalyst is described. In this method, however, there is a problem that the catalyst activity is remarkably low. In addition, there is no description or no suggestion of a method for producing xcex3-butyrolactone effectively by the dehydrogenation of 1,4-butanediol and successive intramolecular cyclization.
The reaction requiring a large amount of the hydrogen acceptor is extremely disadvantageous for industrial practice. In addition, since the hydrogen acceptor is converted to other compound through the dehydrogenation of the alcohol, the acceptor cannot be reused. Therefore, the method is regarded to be industrially impractical.
Moreover, there are described methods for producing xcex3-butyrolactone by dehydrogenating 1,4-butanediol in a vapor phase using copper-chromiummanganese catalyst or copper-chromium-zinc catalyst in Japanese Patent Publication No. 17954/1992 or using a catalyst containing copper, chromium and barium in Japanese Patent Laid-Open No. 232874/1991. These methods, however, do not solve the problems of selectivity and deterioration of the catalysts, or, owing to the vapor phase process, it is difficult to avoid the limitation derived from the equilibrium with the reverse reaction and the problems of the selectivity and the deterioration of the catalyst can be not completely solved.
An object of the invention is to provide a method for producing a carbonyl compound by dehydrogenating an alcohol, wherein the carbonyl compound is produced industrially advantageously at a good selectivity in high yields under mild reaction conditions.
Furthermore, another object of the invention is to provide a method for producing xcex3-butyrolactone industrially advantageously at a good selectivity in high yields under mild reaction conditions by dehydrogenation of 1,4-butanediol and successive cyclization.
As a result of the extensive studies for solving the above problems, the present inventors have found that a complex compound catalyst comprising ruthenium and an organic phosphine wherein aliphatic carbons are bonded to two or more of the three bonding hands of the phosphorus atom can be used as a catalyst for efficiently dehydrogenating an alcohol to produce a carbonyl compound. Especially, they have found that the above complex compound catalyst can be used as a suitable catalyst for producing xcex3-butyrolactone from 1,4-butanediol. The invention has been accomplished based on the above findings.
Namely, a gist of the invention is a method for producing a carbonyl compound, which comprises dehydrogenating an alcohol in the presence of a complex compound catalyst comprising ruthenium and an organic phosphine wherein aliphatic carbons are bonded to two or more of the three bonding hands of the phosphorus atom.
Moreover, another gist of the invention is a method for producing xcex3-butyrolactone, which comprises dehydrogenating 1,4-butanediol in the presence of a complex compound catalyst comprising ruthenium and an organic phosphine wherein aliphatic carbons are bonded to two or more of the three bonding hands of the phosphorus atom.
The catalyst for use in the invention is a complex compound catalyst comprising ruthenium and an organic phosphine wherein aliphatic carbons are bonded to two or more of the three bonding hands of the phosphorus atom. The catalyst may be prepared beforehand and used for the reaction, or each component constituting the catalyst may be incorporated into the reaction system to form the catalyst in the reaction system.
The form of ruthenium metal to be fed is not particularly limited and may be metal ruthenium or a ruthenium compound. Examples of the ruthenium compound include oxides, hydroxides, inorganic acid salts, organic acid salts, complex compounds, and the like, and specific examples include ruthenium dioxide, ruthenium tetraoxide, ruthenium hydroxide, ruthenium chloride, ruthenium bromide, ruthenium iodide, ruthenium nitrate, ruthenium acetate, tris(acetylacetonato)ruthenium, sodium hexachlororuthenate, dipotassium tetracarbonylruthenate, pentacarbonylruthenium, cyclopentadienyldicarbonylruthenium, dibromotricarbonylruthenium, chlorotris(triphenylphosphine)hydridoruthenium, tetra(triphenylphophine)dihydridoruthenium, tetra(trimethylphophine)dihydridoruthenium, bis(tri-n-butylphosphine)tricarbonylruthenium, tetrahydridododecacarbonyltetraruthenium, dodecacarbonyltriruthenium, dicesium octadecacarbonylhexaruthenate, tetraphenylphosphonium undecacarbonyl hydridotriruthenate, and the like. Commercially available compounds may be used as these compounds, or they may be synthesized according to known methods.
The organic phosphine for use in the invention is a phosphine wherein aliphatic carbons are bonded to two or more of the three bonding hands of the phosphorus atom. Examples of the organic phosphine include a trialkylphosphine wherein alkyl groups are bonded to all the three bonding hands of the phosphorus atom, a dialkylarylphosphine wherein alkyl groups are bonded to two of the three bonding hands of the phosphorus atom and an aryl group is bonded to the remaining one hand, and the like. One or two or more phosphorus atom(s) may be present in one molecule of the organic phosphine, and the phosphorous atom may be monodentate or polydentate toward ruthenium.
The alkyl group is a saturated or unsaturated, linear, branched chain or cyclic aliphatic hydrocarbon having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, which may be substituted. The substituent of the alkyl group is not particularly limited but, for example, an aromatic hydrocarbon such as phenyl, tolyl, and the like may be mentioned. Specific examples of such alkyl group include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, n-pentyl, n-hexyl, 2-methylpentyl, 2-ethylbutyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decanyl, benzyl, and the like.
The aryl group is an aromatic hydrocarbon having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, which may be substituted. The substituent of the aromatic hydrocarbon includes alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, etc.; alkoxy groups such as methoxy, ethoxy, etc.; halogen atoms such as chlorine, bromine, etc.; nitro group; sulfone groups; and the like. Specific examples of such aryl group include phenyl, o-, m-, p-tolyl, o-, m-, p-methoxyphenyl, n-, sec-, tert-butyl, o-, m-, p-chlorophenyl, naphthyl, and the like.
In addition, two or more alkyl groups may be combined to form an alkylene group.
In the organic phosphine of the invention, the above functional groups bonded to the phosphorus atom may be the same or different and any two or three groups may form a ring structure. Moreover, the carbon bonded to the phosphorus group may be primary or secondary, but preferably primary.
Examples of the trialkylphosphine having the above alkyl groups include trialkylphosphines having one phosphorus atom in one molecule such as tri(n-decanyl)phosphine, tri(n-nonyl)phosphine, tri(n-octyl)phosphine, tri(n-heptyl)phosphine, tri(n-hexyl)phosphine, tricyclohexylphosphine, tri(n-pentyl)phosphine, tri(n-butyl)phosphine, tri(i-butyl)phosphine, tri(n-propyl)phosphine, tri(i-propyl)phosphine, triethylphosphine, trimethylphosphine, dimethyl(n-octyl)phosphine, di(n-octyl)methylphosphine, dimethyl(n-heptyl)phosphine, di(n-heptyl)methylphosphine, dimethyl(n-hexyl)phosphine, di(n-hexyl)methylphosphine, dimethylcyclohexylphosphine, dicyclohexylmethylphosphine, dimethylbutylphosphine, di(n-butyl)methylphosphine, tribenzylphosphine, etc.; trialkylphosphines having two or more phosphorus atoms in one molecule such as 1,1,2,2-tetrakis(dimethylphosphino)ethane, 1,1,2,2-tetrakis(dimethylphosphino)propane, 1,1,2,2-tetrakis(dimethylphosphino)butane, 1,1,2,2-tetrakis(dioctylphosphino)ethane, 1,1,2,2 tetrakis(dioctylphosphino)propane, 1,1,2,2-tetrakis(dioctylphosphino)butane, 1,1,2,2-tetrakis(dihexyl phosphino)ethane, 1,1,2,2-tetrakis(dihexylphosphino)propane, 1,1,2,2-tetrakis(dihexylphosphino)butane, 1,1,2,2-tetrakis(dibutylphosphino)ethane, 1,1,2,2-tetrakis(dibutylphosphino)propane, 1,1,2,2-tetrakis(dibutylphosphino)butane, etc.; phosphines wherein phosphorus atom(s) is ring-forming element(s), such as 1,1-diphosphinane, 1,4-dimethyl-1,4-diphosphinophane, 1,3-dimethylphosphorinane, 1,4-dimethylphosphorinane, 8-methyl-8-phosphinobicyclooctane, 4-methyl-4-phosphotetracyclooctane, 1-methylphospholane, 1-methylphosphonane 1,4-diphosphabicyclo[2.2.2]octane, 1,3-dimethylphosphorinane, 1,4-dimethylphosphorinane, 1-methylphosphonane, 1-methylphospholane, 1-methylphosphorinane, 1-phosphabicyclo[2.2.2]octane, 1-phosphabicyclo[2.2.1]-heptane, etc.; and the like.
Among them, preferred are trialkylphosphines having one phosphorus atom in one molecule, such as tri(n-decanyl)phosphine, tri(n-nonyl)phosphine, tri(n-octyl)phosphine, tri(n-heptyl)phosphine, tri(n-hexyl)phosphine, tri(n-pentyl)phosphine, tri(n-butyl)phosphine, tri(n-propyl)phosphine, triethylphosphine, trimethylphosphine, dimethyl(n-octyl)phosphine, di(n-octyl)methylphosphine, dimethyl(n-heptyl)phosphine, di(n-heptyl)imethylphosphine, dimethyl (n-hexyl) phosphine, di (n-hexyl) methylphosphine, etc.
Examples of the dialkylarylphosphine include monophosphines such as dimethylphenylphosphine, diethylphenylphosphine, di(n-propyl)phenylphosphine, di(i-propyl)phenylphosphine, di(n-hexyl)phenylphosphine, di(n-octyl)phenylphosphine, dimethyltolylphosphine, diethyltolylphosphine, di(n-propyl)tolylphosphine, di(i-propyl) tolylphosphine, di(n-hexyl) tolylphosphine, di(n-octyl)tolylphosphine, etc.; polyphosphines such as methylphenylphosphinoethane, ethylphenylphosphinoethane, methylphenylphosphinopropane, etc.; and the like.
With regard to the availability of the above organic phosphines, commercially available phosphines may be generally used but the phosphines can be synthesized according to known methods, if necessary, and used. The synthetic methods for the organic phosphines include Grinard reaction and the like as described in Jikken Kagaku Koza, fourth edition, Vol.24, page 229; H. Hibbert, Chem. Ber., 39, 160 (1906), and so forth, for example. Moreover, a desired organic phosphine may be synthesized by reacting a phosphine having a phenyl group, such as a dialkylphenylphosphine, with lithium metal and further reacting with an alkyl bromide to replace the phenyl group with the alkyl group.
The amount of the organic phosphine to be used is, relative to ruthenium metal, in an atom ratio of phosphorus atom/metal ranging usually from 0.1 to 1000, preferably from 1 to 100. However, in the case of using a compound containing a phosphine where two or more aryl groups are bonded to the phosphorus atom, such as triphenylphosphine, as a ruthenium metal-feeding compound, it is preferable to increase the atom ratio of phosphorus atom/metal so that this-phosphine is replaced with the above organic phosphine.
The characteristic feature of the catalyst for use in the invention is to comprise ruthenium and an organic phosphine wherein aliphatic carbons are bonded to two or more of the three bonding hands of the phosphorus atom as described above, but the catalyst may further comprise a neutral ligand or the like as an optional component. Examples of the optional component include hydrocarbons having an ethylenic unsaturated bond, such as ethylene, propylene, butene, cyclopentene, cyclohexene, butadiene, cyclopentadiene, cyclooctadiene, norbornadiene, etc.; ethers such as diethyl ether, anisole, dioxane, tetrahydrofuran, etc.; carboxylic acids or carboxylic acid esters such as propionic acid, caproic acid, butyric acid, benzoic acid, methyl benzoate, ethyl acetate, ally acetate, etc.; dimethyl sulfide; organic phosphorus compounds such as tributylphopsphine oxide, ehtyldiphenylphosphine oxide, triphenylphosphine oxide, trioctylphosphine oxide, diethylphenyl phosphinate, diphenylethyl phosphinate, triethyl phosphate, triphenyl phosphite, trioctyl phosphate, hexamethylphosphoric triamide, etc; and further, carbon monoxide, ethylene glycol, carbon disulfide, caprolactam, and the like. Therefore, in some cases, a starting material for the reaction, a reaction product, or a solvent may become a component of the catalyst.
Furthermore, the catalyst may be used in the form of a cationic complex using a conjugate base of an acid whose pKa is less than 2. Preferable results such as the stabilization of the catalyst, the enhancement of the activity, and the like may be obtained by the use of the cationic complex.
As the compound providing the conjugate base of an acid whose pKa is less than 2, a Brxcfx86nsted acid whose pKa is less than 2 or a salt thereof may be usually used. Specific examples include inorganic acids such as nitric acid, perchloric acid, borofluoric acid, hexafluorophosphoric acid, fluorosulfonic acid, etc.; organic acids such as trichloroacetic acid, dichloroacetic acid, trifluoroacetic acid, dodecylsulfonic acid, octadecylsulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, tetra(pentafluorophenyl)boronic acid, sulfonated styrenedivinylbenzene copolymer, etc.; and alkali metal salts, alkaline earth metal salts, ammonium salts and silver salts of these inorganic acids and organic acids; and the like. Moreover, compounds capable of providing conjugate bases of these acids, such as acid halides, acid anhydrides, esters, acid amides and the like may be also used. These compounds providing conjugate bases of acids whose pKa is less than 2 may be used in an amount of usually 1000 or less moles, preferably 100 or less moles, per mole of ruthenium metal.
In the case of using the catalyst of the invention prepared beforehand, the preparing method is not particularly limited but, as one example, an alcohol solution of a complex compound catalyst is formed by incorporating tris(acetylacetonato)ruthenium and 5 to 20 molar equivalents of a trialkylphosphine into an alcohol of a starting material for reaction and stirring the whole under a hydrogen atmosphere. Moreover, its conversion to a cationic complex can be effected by adding a compound providing a conjugate base of an acid whose pKa is not more than 2 to the solution containing the catalyst obtained in the above, in an amount of 0.1 to 20 moles, preferably 1 to 10 moles, per mole of ruthenium. The cationic complex compound catalyst can be also synthesized by adding, to an alcohol of a starting material for reaction, tris (acetylacetonato) ruthenium, a trialkylphosphine, and a compound providing a conjugate base of an acid whose pKa is not more than 2.
The alcohol of a starting material for reaction may be a monohydric alcohol or a polyhydric alcohol as far as it has primary or secondary hydroxyl group(s). Moreover, the alcohol may be saturated or unsaturated, and may have a substituent. Examples of some monohydric alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-octanol, 3-octanol, 4-octanol, 1-nonanol, 2-nonanol, 3-nonanol, 4-nonanol, 5-nonanol, 1-decanol, 2-decanol, 3-decanol, 4-decanol, 5-decanol, allyl alcohol, 1-butenol, 2-butenol, 1-pentenol, 2-pentenol, 1-hexenol, 2-hexenol, 3-hexenol, 1-heptenol, 2-heptenol, 3-heptenol, 1-octenol, 2-octenol, 3-octenol, 4-octenol, 1-nonenol, 2-nonenol, 3-nonenol, 4-nonenpl, 1-decenol, 2-decenol, 3-decenol, 4-decenol, 5-decenol, cyclohexanol, cyclopentanol, cycloheptanol, 1-phenythyl alcohol, 2-phenythyl alcohol, methanolamine, ethanolamine, and the like. By the way, in the case of an unsaturated alcohol, the unsaturated bond may be at any position.
Examples of the polyhydric alcohol include dihydric alcohols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1-hydroxymethyl-2-hydroxyethylcyclohexane, 1-hydroxy-2-hydroxypropylcyclohexane, 1-hydroxy-2-hydroxyethylcyclohexane, 1-hydroxymethyl-2-hydroxyethylbenzene, 1-hydroxymethyl-2-hydroxypropylbenzene, 1-hydroxy-2-hydroxyethylbenzene, 1,2-benzylmethylol, 1,3-benzylndimethylol, and the like. When an alcohol having two primary hydroxyl groups is used as a starting material, a polyester may be formed in some cases through intermolecular ester linkage via the reaction process, but in the case that 2 to 4 carbon atoms are present between the carbon atoms to which the primary hydroxyl groups are bonded, a lactone compound can be formed through intramolecular cyclization.
Among the above starting alcohols, preferred are alcohols having 4 or more carbon atoms, and more preferred are diols having 4 or more carbon atoms, such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, and the like. In particular, the invention is suitable for dehydrogenation and cyclization for producing xcex3-butyrolactone from 1,4-butanediol.
The hydrogenation of an alcohol according to the invention is carried out usually without solvent, i.e., in the absence of a solvent other than the alcohol of the starting material and a carbonyl compound of the product, but other solvent can be also used, if desired. Examples of the solvent include ethers such as diethyl ether, anisole, tetrahydrofuran, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, etc.; alcohols such as methanol, ethanol, n-butanol, benzyl alcohol, ethylene glycol, diethylene glycol, etc.; phenols such as phenol, etc.; carboxylic acids such as formic acid, acetic acid, propionic acid, toluic acid, etc.; esters such as methyl acetate, butyl acetate, benzyl benzoate, etc.; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, L tetralin, etc.; aliphatic hydrocarbons such as n-hexane, n-octane, cyclohexane, etc.; halogenated hydrocarbons such as dichloromethane, trichloroethane, chlorobenzene, etc.; nitro compounds such as nitromethane, nitrobenzene, etc.; carbamides such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, etc.; other amides such as hexamethylphosphoric triamide, etc.; ureas such as N,N-dimethylimidazolidinone, etc.; sulfones such as dimethyl sulfone, etc.; sulfoxides such as dimethyl sulfoxide, etc.; lactones such as xcex3-butyrolactone, caprolactone, etc.; carbonic acid esters such as dimethyl carbonate, ethylene carbonate, etc.; polyethers such as triglyme, tetraglyme, etc.; and the like.
Among them, preferred are ethers, polyethers, and the like.
The reaction is carried out at the temperature of usually 20 to 350xc2x0 C., preferably 100 to 250xc2x0 C., more preferably 150 to 220 C. The catalyst concentration may be in the range wherein industrially desirable activity is shown, but the catalyst may be incorporated into the reaction system in the range of 0.0001 to 100 mol/L, preferably 0.001 to 10 mol/L as ruthenium metal relative to the reaction liquid. The reaction proceeds generally as a homogeneous catalytic reaction.
The catalyst for use in the invention is capable of dehydrogenating an alcohol at a high activity and a high selectivity. Therefore, it is not necessary to incorporate a hydrogen-acceptor in the reaction system but it may be incorporated, if desired. Examples of the hydrogen-acceptor include carbonyl, alkene, or alkyne compounds, such as acetone, diphenylacetylene, vinyl methyl ketone, benzalacetone, ethyl methyl ketone, p-benzoquinone, nitrobenzene, acetonitrile, vinyl chloride, benzonitrile, acetaldehyde, formaldehyde, butyraldehyde, benzaldehyde, etc., or the like.
The reaction pressure may be any pressure as far as the reaction system is maintained a liquid phase, but since the dehydrogenation of an alcohol according to the invention is a hydrogen-forming reaction, it is preferable to carrying out the reaction with removing the hydrogen into outside of the system. Therefore, it is preferred to carry out the reaction in an open system. In the case of carrying out the reaction in a closed system, the atmosphere is preferably an inert gas such as nitrogen, argon, helium, carbon dioxide, or the like. The reaction can be carried out as a batch process or a continuous process. The reaction product solution is subjected to distillation to remove a carbonyl compound formed, and since the catalyst is dissolved in the remaining solution, it is recovered and can be used at next reaction as the catalyst.
The carbonyl compounds, especially lactone compounds obtainable by the method of the invention can be reacted with alkylamines to produce pyrrolidones. For example, N-methylpyrrolidone can be produced by reacting xcex3-butyrolactone with methylamine and can be industrially used as detergent, solvent, or the like, widely. The production methods for methylamine and N-methylpyrrolidone are not particularly limited and usual methods themselves already known may be adopted. The methods described in U.S. Pat. No. 3,387,032, Japanese Patent Laid-open No. 12514/1997, and so forth may be mentioned as the methods for producing methylamine, but usually, it can be produced by reacting methanol and ammonia in the presence of a catalyst such as silica and/or alumina, zeolite, or the like. As the method for producing N-methylpyrrolidone, for example, method described in Japanese Patent Publication No. 18751/1972 or 78305/1994, and so forth may be used, and the compound can be obtained by reacting mono-, di- and/or trimethylamine with xcex3-butyrolactone under heating.
Moreover, the carbonyl compounds, especially xcex3-butyrolactone obtainable by the method of the invention may be used as a solvent for electrolytes as described in Japanese patent Laid-Open No. 97062/1999, 135374/1999, and so forth; a washing solution for polyurethanes as described in Japanese Patent Laid-Open No. 176695/1997 and so forth; and the like.